Cod sursa(job #2888243)

Utilizator buzu.tudor67Tudor Buzu buzu.tudor67 Data 10 aprilie 2022 20:49:05
Problema Flux maxim Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 2.85 kb
#include <bits/stdc++.h>
using namespace std;

class Graph{
public:
    const int N;
    vector<vector<int>> neighbors;
    vector<vector<int>> capacity;

public:
    Graph(const int& N): N(N){
        neighbors.resize(N);
        capacity.assign(N, vector<int>(N));
    }

    void addEdge(int x, int y, int c){
        neighbors[x].push_back(y);
        neighbors[y].push_back(x);
        capacity[x][y] = c;
    }
};

class Dinic{
private:
    const Graph& G;
    const int N;
    const int SRC;
    const int DEST;
    const int INF = 1e8;
    vector<vector<int>> f;
    vector<int> dist;
    vector<int> startEdgeIdx;

    int bfs(){
        fill(dist.begin(), dist.end(), INF);
        
        queue<int> q;
        q.push(SRC);
        dist[SRC] = 0;
        while(!q.empty()){
            int node = q.front();
            q.pop();

            if(dist[node] == dist[DEST]){
                break;
            }

            for(int nextNode: G.neighbors[node]){
                int remainingCapacity = G.capacity[node][nextNode] - f[node][nextNode];
                if(remainingCapacity > 0 && dist[nextNode] == INF){
                    dist[nextNode] = 1 + dist[node];
                    q.push(nextNode);
                }
            }
        }

        return (dist[DEST] != INF);
    }

    int dfs(int node, int minDelta){
        if(node == DEST){
            return minDelta;
        }
        for(; startEdgeIdx[node] < (int)G.neighbors[node].size(); ++startEdgeIdx[node]){
            int nextNode = G.neighbors[node][startEdgeIdx[node]];
            int remainingCapacity = G.capacity[node][nextNode] - f[node][nextNode];
            if(remainingCapacity > 0 && dist[node] + 1 == dist[nextNode]){
                int delta = dfs(nextNode, min(minDelta, remainingCapacity));
                if(delta > 0){
                    f[node][nextNode] += delta;
                    f[nextNode][node] -= delta;
                    return delta;
                }
            }
        }
        return 0;
    }

public:
    Dinic(const Graph& G, const int& SRC, const int& DEST):
          G(G), N(G.N), SRC(SRC), DEST(DEST){
    }

    int computeMaxFlow(){
        f.assign(N, vector<int>(N, 0));
        dist.resize(N);
        startEdgeIdx.resize(N);

        int maxFlow = 0;
        while(bfs()){
            fill(startEdgeIdx.begin(), startEdgeIdx.end(), 0);
            int delta = INF;
            while(delta > 0){
                delta = dfs(SRC, INF);
                maxFlow += delta;
            }
        }

        return maxFlow;
    }
};

int main(){
    ifstream cin("maxflow.in");
    ofstream cout("maxflow.out");

    int N, M;
    cin >> N >> M;

    Graph G(N);
    int x, y, c;
    for(int i = 0; i < M; ++i){
        cin >> x >> y >> c;
        G.addEdge(x - 1, y - 1, c);
    }

    cout << Dinic(G, 0, N - 1).computeMaxFlow();

    cin.close();
    cout.close();
    return 0;
}